Devices for detecting objects in the surroundings of a vehicle include those device which monitor the blind spot of a vehicle, which are known as blind spot detection systems (BSD systems). These systems are generally used for electronically detecting objects in the surroundings of the vehicle which are difficult for the driver to observe without turning his/her head to the side. Such head turning (looking over the shoulder) is not possible in many cases because of the associated neglect of the traffic situation ahead. In particular on multi-lane roads, a BSD system signals to the driver of a vehicle when another vehicle (object) is passing at a lower differential velocity, thereby remaining in the blind spot to the right or left of the vehicle longer than only an instant. The danger of an accident because of overlooking other vehicles during a lane change may be reduced due to such information being available to the driver.
According to the known art, sensors for detecting external vehicles (objects) or for evaluating collision scenarios are used in vehicles. These sensors use ultrasonic, radar, or light waves to detect the existence of objects in a contactless manner and are also able to measure the vehicle's distance to the objects.
A device for detecting objects in the blind spot of a vehicle described in U.S. Pat. No. 5,583,495 includes individual ultrasonic waves which are generated at a predefined angle via a signal generator. The ultrasonic waves, subsequently reflected or scattered by a potential object, are received and amplified by an ultrasonic receiver. A point in time of a potential collision between the object and the host vehicle is calculated from this ultrasonic signal, the vehicle's velocity, and the vehicle's steering angle. Moreover, the device described in U.S. Pat. No. 5,583,495 has means for communicating with the driver which, in the event of a likely collision with an object situated in the blind spot, trigger an alert or inform the driver in another suitable way.
A disadvantage of the known ultrasound-based BSD systems is their particularly long response time. Due to the lower propagation rate of sound waves (compared to radar waves or light waves), the measuring time of ultrasound-based BSD systems is longer than the measuring time of comparable radar-based or light wave-based BSD systems. The response time of the system is longer due to the longer measuring time so that, in the event of a potential collision with an object in the blind spot, the appropriate warning to the driver is delayed. However, the use of faster radar sensors or light sensors entails a substantial cost disadvantage.
Therefore, it is an object of the present invention to provide a method and a device for detecting objects in the surroundings of a vehicle via which a shorter measuring time and consequently a shorter response time are facilitated for alerting the driver in the event of an imminent collision with an object in the vehicle's surroundings. This makes it possible in particular to use cost-effective ultrasonic sensors.